hollow

The lining attached to
both the spine of the text block and the inside of
the spine of the covering material. It is usually
constructed of kraft paper, and consists of a
folded sheet, one section of which is glued to the
spine of the text block and the other to the
covering material. There are many variations of
the hollow, however; for example, see: ONE ON AND TWO OFF ,
or TWO ON AND ONE
OFF , The purpose of the hollow is to assist
in the opening of the book much in the same manner
as th SPRING-BACK
of a blankbook, though with much less force. The
thickness of the paper used for the hollow depends
on the size and thickness of the book and the
thickness of the paper and sections of the book.
(81 , 261 )